It is known to provide blade arrangements that are used in turbomachines such as gas turbines with damping elements. These serve the purpose of damping undesired flexural and torsional vibrations that may occur during operation in the turbomachine as a result of various inducing factors. In this way, instances of HCF damage (abbreviation for “High Cycle Fatigue”) that are caused by high vibration amplitudes and could lead to premature material fatigue, and to a consequently shortened service life of the blades or the blade arrangement, can be avoided. The damping elements are in this case arranged between the individual blades. Generally used as damping elements are loose bodies which, in the state of rest, initially lie between the blade roots of the blades on the rotor or on corresponding supporting structures and during operation of the rotor are pressed against the underside of the blade platforms of adjacent blades as a result of the centrifugal force acting in the radial direction. Each damping element is in this case in contact with both adjacent blade platforms at the same time. This allows the kinetic energy of a relative movement between the blades that is induced by vibrations to be converted into thermal energy, as a result of the friction between the respective blade platforms and the adjoining damping element. This damps the vibrations and leads altogether to a reduced vibrational loading of the blade arrangement.
In the case of older turbomachines, blade airfoil vibrations were usually suppressed with the aid of stiffening elements that coupled the blade airfoils directly to one another. Design solutions for this are disclosed by patent specifications DE 819 242 C and U.S. Pat. No. 1,618,285 A.
The document EP 1 154 125 A2 discloses a blade arrangement in which at least two damping elements are arranged one behind the other between adjacent blades in the circumferential direction of the rotor, in order to achieve effective damping of the blade arrangement as a whole. The damping elements disclosed in this document are configured in a form differing from each other, in order to be able as far as possible to damp a large number of different modes of vibration. By way of the contact regions forming between the damping elements and the blades, and furthermore by way of the contact regions forming between the individual damping elements, vibrational energy can be converted into thermal energy for vibration damping by frictional action. However, the contact regions forming between the individual damping elements have only the form of a linear contact, with which there is only a moderate associated damping effect.
Other forms of dampers are likewise known, for example according to FR 1263 677 A the arrangement of a multiplicity of balls between two adjacent rotor blades.